Liquid-containing electrical bushing



g- 5, 1 5 E. A. LINK 2,846,495

LIQUID-CONTAINING ELECTRICAL BUSHING Filed June 6, 1951 2 Sheets-Sheet 1 IN VEN TOR. 30 EDI KIN A LINK BY 33 J2 -ZZ M F ATTORNEY Aug. 5, 1958 E. A. LINK LIQUID-CONTAINING ELECTRICAL BUSHING 2 Sheets-Sheet 2 Filed June 6. 1951 INVENTOR. EDWIN A. LINK ATTO/F/VE Y United States Patent LIQUID-CONTAINING ELECTRICAL BUSHING Edwin A. Link, Milwaukee, Wis, assignor, by mesne assigninents, to R T & E Corporation, Waukesha, Wis, a corporation of Wisconsin Application June 6, 1951, Serial No. 230,160

9 Claims. (Cl. 174-31) This invention relates to liquid-containing electrical bushings.

it is a well-known fact that so-called oil-filled electrical bushings have numerous advantages over the so-called solid bushings. Some of the more important advantages of the oil-filled bushings are that they minimize the possibility of radio interference, reduce the possibility of internal discharges, and that they are not injured by excessive high potentials.

The realization of the advantages of oil-filled bushings has led to the production of numerous types of these bushings and to the best of my knowledge, practically all of these bushings have been sealed to prevent the loss of oil and many have incorporated rather costly structures to insure the maintenance of the proper amount of oil in the bushing. While many of these oil-filled bushings have proven satisfactory in operation, they have been uniformly more expensive to manufacture due to structural features and assembly costs.

Another well established fact is that the combination of oil and insulating material in oil-filled bushings produces a device having excellent characteristics for withstanding high voltages and this has led some manufacturers to produce oil-filled bushings of this type in spite of the fact that the structural and assembly costs of such devices have been materially increased by so doing.

The present invention provides a new and improved liquid-containing electrical bushing which, due to its simplicity of constructon and method of fabrication, affords a device capable of being produced at an extremely low cost when compared with the cost of similar devices operating at the same uniformly high degree of efficiency afforded by the bushing of the present invention.

The primary object of the present invention resides in the provision of a new and improved liquid-containing electrical bushing.

Another object of the invention resides in the provision of a new and improved liquid-containing electrical bushing constructed in a manner to reduce corona and substantially eliminate radio interference.

Another object of the invention resides in the provision of a new and improved liquid-containing electrical bushing having materially increased dielectric strength.

Another object of the invention resides in the provision of a new and improved liquid-containing electrical bushing having the optimum electrical properties with a minimum liquid capacity.

Another object of the invention resides in the provision of a new and improved liquid-containing electrical bushing wherein the necessity for liquid seals is eliminated.

Another object of the invention resides in the provision in an electrical bushing of wick means for maintaining liquid in the bushing.

Another object of the invention resides in the proviaion in an electrical bushing of new and improved means in the form of a porous mass capable of being impregnated or saturated with liquid for maintaining liquid in the bushing.

Another specific object of the invention resides in the provision of a new and improved liquid-containing electrical bushing which is simple in form, economical in cost and one which provides excellent operating characteristics.

Other objects and advantages will become apparent from the following description of an illustrative embodiment of the present invention.

In the drawings:

Figure l is a vertical sectional view of an unsealed liquid-containing electrical bushing embodying the teachings of the present invention and showing the arrangement of parts and more particularly the wick means for maintaining liquid in the bushing;

Fig. 2 is a top plan view of the bushing shown in Fig. 1;

Fig. 3 is a horizontal sectional view through the bushing, taken on the line 33 of Fig. 1, showing the liquid-saturated wick surrounding the current conductor;

Fig. 4- is a bottom plan view of the bushing shown in Fig. 1 with a portion broken away to show the passage through which liquid may be supplied to saturate the wick to maintain liquid in the bushing;

Fig. 5 is a composite view showing the electrical conductor, a blanket of wick material, the conductor partially wrapped with the wick material, and the conductor completely wrapped ready for insertion into the conductor receiving passage in the body portion of a bushing;

Fig. 6 is a view showing the body of the bushing and a wick-wrapped conductor both positioned on a holding device including flexible wick contacting elements preparatory to effecting the desired assembly of the parts;

Fig. 7 is a view similar to Fig. 6 showing the body of the bushing and wick-wrapped conductor on the holding device after their assembly has been effected by drawing the bushing over the wick-wrapped conductor;

Fig. 8 is an enlarged fragmentary sectional view showing portions of the holding device, body of the bushing, and the wick-wrapped conductor and illustrating the cooperative relationship of the several elements for effecting the compression of the wick material and the introduction of the wick-wrapped conductor into the conductor receiving passage of the bushing; and

Fig. 9 is a horizontal sectional view through the bushing, taken on the line 9-9 of Fig. 8, showing the position of the flexible wick contacting elements with relation to the compressible wick in effecting the application of lateral pressure upon the wick to compress it to effect its introduction with the conductor into the conductor receiving passage in the body portion of the bushing.

Referring more particularly to Fig. 1 of the accompanying drawings, it will be noted that the liquid-containing electrical bushing til, chosen for illustrative purposes and embodying the teachings of the present invention, comprises, generally, a conventional porcelain insulator body portion or housing 11 having an axially disposed passage 12 adapted to receive an electrical conductor 13 preferably, but not necessarily, in the form of a stud having its ends projecting beyond the confines of the passage 12 and having its intermediate portion surrounded by a mass of porous dielectric material 14 such, for example, as a blanket of fiber glass adapted to fill that portion of the passage 1's not occupied by the conductor 13.

The conventional body portion or housing 11 of the bushing 10 is adapted for mounting either on the wall or cover of a power transformer. The housing 11, chosen for illustrative purposes, includes a horizontally disposed gasket seat 15, surrounded by a depending flange l6, located at the juncture between the upper or exposed portion and the lower or housed portion of the bushing Elli. The flange 16 and the gasket seat cooperate to form a recess adapted to receive a sealing. gasket 17, formed of suitable insulating material, adapted to en circle the depending portion of the bushing 10 and a bush ing receiving aperture 13 formed in a raisedportion 19 of a tank cover 29 to form a seal therebctween when the bushing is secured to the tank cover.

The upper portion of the bushing Ml is completed byv i the application of a line terminal connector 21 having an adjustably mounted current conducting lead clamping member 22 to the upper end of the conductor 13 which projects beyond the confines of the conductor receiving passage 12 in the housing 11 of the bushing. The connector 21 is provided with a gasket receiving recess 23 in its lower surface from which a centrally arranged upwardly directed threaded hole 24 extends into the body of the connector. A sealing gasket 25, formed of suitable insulating material, is positioned with in the recess 23 and serves to seal the joint between the connector 21 and the upper end of the housing 11 when the connector is attached to the conductor 13 through the threaded engagement between the hole 24 and the upper end of the conductor 13.

The lower portion of the bushing 10 is completed by the positioning of a jacket element or sleeve 26 over the lower portion of the bushing 10. The jacket or sleeve 26 is preferably formed of porcelain or other suitable insulating material and is adapted to surround the lower portion of the bushing 10 to serve a dual purpose. Firstly, it is constructed in a manner to lie in spaced relationship with the portion of the bushing which it surrounds and cooperates therewith to provide a liquid-containing chamber or reservoir 27 and, secondly, it affords a means by which the bushing 16 is retained in position on the tank cover 2'0. A gasket 28 formed of fiber or other suitable material is adapted for positioning between the upper end of the jacket 26 and the under surface of the raised portion 157 of the tank cover 24 to provide a cushion and seal between the tank cover and the bushing. A similar gasket 29 is adapted for positioning on the lower end of the jacket 26 between it and a metal washer 3t] receivable over the lower threaded end of the conductor 13.

To secure the bushing MD on the tank cover 20, the

lower portion of the bushing is inserted into the bushing receiving aperture 18 and lowered until the gasket 17 is resting upon the top surface of the raised portion 19 of the tank Ell. The gasket 23 is then slid upwardly over the lower portion of the bushing to a position against the under surface of the raised portion of the tank cover. The jacket or sleeve 26 is then slid upwardly over the lower portion of the bushing until it contacts the gasket 28; the gasket 29 is placed on the lower end of the bushing; the washer 39 is then threaded over the lower end of the conductor 13 and a nut 31 is then tightened on the lower threaded end of the conductor 13 to draw the several parts together and releasably retain the bushing 16 properly upon the tank cover 26.

A terminal 32 secured to one end of a current conducting lead 33 may be positioned on the projecting portion of the lower end of the conductor 13 and retained in electrical connection therewith by the application of nut 34.

While the structural features of the electrical bushing have been mentioned in a general way in the foregoing portion of the specification, there are a few of the structural features that are of sufficient importance to warrant special consideration in the form of amplified remarks concerning their function and more of operation. First among these features lies in the mass of porous dielectric material 14, which surrounds the conductor 13 and substantially fills that portion of the conductor receiving passage 12 not accupied by the conductor. This porous mass of dielectric material 14 forms a wick, which, by reason of its inherent characteristics, provides a simple and sure means for maintaining the wick thoroughly saturated with liquid drawn by means of capillary action from a suitable liquid reservoir into which the lower portion of the wick extends. The fact that the wick 14 is thus retained saturated with liquid provides a simple and effective means for maintaining the conductor receiving passage 12 of the bushing 10 substantially filled with liquid at all times to thus insure the provision of a liquid-containing electrical bushing having materially in ed dielectric strength and the optimum electrical es satisfied with a minimum liquid capacity which is sfied at all times through the capillary action of the wick. While l have chosen to show the wick 14, in the accompanying drawings, as a blanket of compressible fiber glass, it is to be understood that any one of a number of other dielectric materials, having similar characteristics, might be substituted with entirely satisfactory results. The present in-- vention also contemplates the use of a porous or fibrous wick impregnated with liquid so as not to require the necessity of having a liquid reservoir from which the liquid might be drawn.

Another structural feature of the present invention worthy of further consideration is found in the provision of means for maintaining an unsealed bushing or one having a bottom opening substantially filled with liquid. Referring more particularly to Fig. l of the accompanying drawings, it will be noted that the gasket 29, positioned between the bottom end of the bushing 10 and the metal washer 30, is not a complete circle but is provided with an opening or gap 35 which cooperates with the bottom edge of the bushing 10 and the top surface of the metal washer 30 to form a port or passage 36 adapted to pro vide open communication between the liquid reservoir 27 in the bushing 10 and the liquid contained in the trans former tank to which the bushing is attached. With this condition present, it will readily be understood that so long as the liquid level in the transformer tank is maintained above the bottom of the passage 36 the wick 14 will insure the maintaining of the conductor receiving passage 12 substantially filled with liquid through the capillary action of the wick. Obviously, if the wick l4 is presaturated with liquid or if the reservoir 27 has sufficient capacity to saturate the wick 14, the open communication between the reservoir 27 in the bushing 10f and the liquid-containing transformer tank is not essen-- tial to the satisfactory functioning of the device.

Another feature of the present invention worthy of further comment is found in the arrangement of the lower extremity of the wick 14. It will be noted with reference to Fig. 1, that the lower end of the wick 14 projects below the bottom of housing 11 and is contained in partially expanded condition within the confines of the reservoir 27 or that space between the bottom of the housing 11, the top of the metal washer 30 and the inner surface of the jacket or sleeve element 26. This arrangement of the wick 14. insures a relatively large surface of contact be tween the wick and the liquid contained in the reservoir 27 and since the lower extremity of the wick 14 is not compressed it affords an ample supply of liquid to be drawn up the wick by its capillary action to maintain the bushing 10 substantially filled with liquid.

The foregoing description of an illustrative embodiment of the present invention has been confined to the structural aspects of the liquid-containing bushing. The remainder of the description will be directed to the new and improved method of fabricating a liquid-containing electrical bushing.

Referring to Fig. 5 of the accompanying drawings, it will be noted that I have therein illustrated, in a composite view, the method of wrapping the conductor 13 in pressed-and still maintaining the properties of a wick.

adapted to be retained substantially filled with an insulating liquid by means of capillary action. The conductor 13, in the form of a stud, is laid lengthwise along the top longitudinal leading edge of the fiber glass blanket 14. Pressure is then applied to the conductor 13 and it is rolled forwardly on the blanket 14 to compress the same and effect the wrapping of the blanket 14 on the conductor 13. While this operation materially reduces the thickness of the dielectric material, the diameter of the wick-wrapped conductor 13 is still substantially greater than the diameter of the passage 12 in the bushing into which the wick-wrapped conductor 13 is to be inserted. The next step in the fabrication of the bushing comprises the application of the bushing 11) onto a holding structure. The holding structure may assume any of a number of forms but should include essentially a portion adapted to receive the bushing 10, and a portion adapted to receive the wick-wrapped conductor 13, which portion should include a plurality of flexible wick contaeting members responsive to the pressure of the bushing 16 to reduce the diameter of the wick-wrapped conductor 13 by compressing it to a diameter small enough to permit the wick-wrapped conductor to slide into the conductor receiving passage 12 of the bushing 10 as the bushing is drawn over the wicl-wrapped conductor 13 which is retained in the holding structure. For the purpose of illustrating a preferred method of fabricating the liquid-containing electrical bushing, i have chosen to show a holding structure of simple form which is capable of carrying out the desired method of fabrication of the bushing. The holding structure illustrated in Figs. 6 and 7 comprises a bushing receiving portion 40 in the form of a rod having threaded ends. The upper end of the rod 48 is threaded into a mounting plate 41 which in turn is secured to any suitable support 42. The wickwrapped conductor holding portion of the structure comprises a plug 43 having a diameter such that it is capable of being passed through the conductor receiving passage 12 formed in the bushing housing 11. A pair of axially aligned holes 44 and 45 are disposed at opposite ends of the plug 43. The upper hole 44 is threaded to receive the threaded lower end of the rod 40 while the lower hole 45 is not threaded and is large enough to slidably receive a threaded end of the conductor 13. A plurality of flexible wick contacting members 46 are embedded and secured in circumferentially spaced relationship on the plug 43 around the hole 45 and project downwardly from the plug a sufficient distance to reach approximately to the lower end of the wick 14.

To effect the fabrication of the liquid-containing bushing, the upper end of the passage 12 in the bushing housing 11 is placed directly below the lower end of the bushing receiving rod 40 and the bushing is raised on the rod to a position in which the lower threaded end of the rod projects below the bottom of the bushing. The wickwrapped conductor holding portion of the device may then be attached to the lower end of the rod 40 by threading the same into the hole 44 in the plug 43. After the conductor holding portion of the structure has been properly positioned, a wick-wrapped conductor 13 may be positioned in the holding device by inserting one end of the conductor 13 into the hole 45 of the plug 43. The housing 11 of the bushing 1% may then be drawn downwardly over the plug 43 and onto the flexible members 4-6 which contact the outer surface of the wick 14. The pressure of the passage 12 upon the flexible wick-contacting members 46 causes them to move inwardly to effect lateral pressure upon the wick 14 to compress the same to a diameter small enough to permit the housing to slide readily over the compressed wick. The downward movement of the housing is continued until the upper end of the wick reaches the top of the passage 12 in the bushing housing 11. The plug 43 may then be removed from the lower end of the rod 40 and the plug 43 and flexible members 46 may then be withdrawn from the bushing 10 without disturbing the relative position. of any of the parts of the fabricated bushing.

From the foregoing description of the new and improved method of fabricating a liquid-containing electrical bushing it will be apparent that a novel, eflicient and expeditious manner of assembly has been provided which insures against any damage to the wick which might impair its efficient functioning to afford a simple and effective method of maintaining the bushing substantially filled with liquid through the medium of its capillary action.

While the numerous advantages of the present liquidcontaining bushing have been described in considerable detail both as to structure and method of fabrication, it is to be understood that various changes may be made in their embodiments without departing from or sacrificing any of the advantages hereinafter claimed.

I claim:

1. A liquid-containing electrical bushing for partial submersion in a liquid-containing reservoir, said bushing comprising a substantially vertically disposed housing formed of insulating material having its upper end above the level of liquid in the reservoir and including a conductor receiving passage therein extending the full length thereof, an electrical conductor in said passage having its ends projecting ab ve and below said bushing, and a wick comprising a blanket of compressible material surrounding said conductor and substantially filling the space of said passage not occupied by said conductor, said wick having a portion in open communication with liquid in said reservoir and comprising the sole means by which said conductor passage and bushing are maintained substantially filled with liquid elevated from the liquid-containing reservoir through the capillary action of said wick.

2. A liquid-containing electrical bushing constructed as set forth in claim 1, in which the wick is comprised of resilient dielectric material.

3. An unsealed liquid-containing electrical bushing comprising a housing formed of insulating material adapted for substantially vertical positioning with a portion thereof projecting below and the major portion thereof disposed well above a level of liquid in a reservoir, said housing including a conductor receiving passage extending the full length thereof, an electrical conductor in said passage having its ends projecting above and below said bushing, and a wick formed of a sheet of compressible dielectric material surrounding said conductor and substantially filling the space in said passage not occupied by said conductor, said wick having a portion in open communication with the liquid in said reservoir comprising the sole means by which said conductor receiving passage and bushing are maintained substantially filled witht liquid elevated from said liquid containing reservoir through the capillary action of said wick.

4. An unsealed liquid-containing electrical bushing constructed as set forth in claim 3, in which the wick is comprised of a resilient fibrous material.

5. An unsealed liquid-containing electrical bushing constructed as set forth in claim 3, in which the wick is comprised of a porous mass of resilient material.

6. An unsealed liquid-containing electrical bushing constructed as set forth in claim 3, in which the wick comprises a resilient compressible fibrous dielectric material.

7. An unsealed liquid-containing electrical bushing constructed as set forth in claim 3, in which the wick is comprised of a resilient compressible porous mass of dielectric material.

8. A liquid-containing electrical bushing comprising a housing formed of insulating material, an axially disposed conductor receiving passage in said housing, a packet formed of insulating material surrounding a portion of said housing and cooperating therewith to form a liquid-containing reservoir, an electrical conductor positioned in said passage, and a Wick formed of dielectric material surrounding said conductor and substantially filling the space of said passage not occupied by said conductor, said wick comprising the means by which said bushing is maintained substantially filled with liquid drawn from said reservoir.

9. A liquid-containing electrical bushing comprising a housing formed of insulating material, an axially disposed conductor receiving passage in said housing, a jacket formed of insulating material surrounding a portion of said housing and cooperating therewith to form a liquid-containing reservoir, an electrical conductor positioned in said passage, a wick formed of dielectric material surrounding said conductor and substantially filling the space in said passage not occupied by said conductor, a portion of said wick projecting into said liquidcontaining reservoir whereby said bushing is maintained substantially filled with liquid drawn from said reservoir by said wick, and a current-carrying terminal electrically connected to each end of said conductor.

References Cited in the file of this patent UNITED STATES PATENTS Williams May 16, Marsh Sept. 5, Hackethal June 5, Fortescue Feb. 23, Eby May 20, Tebo June 2, Wesseler Aug. 21, Hirshfeld Aug. 22, Austin July 24, Whisler Oct. 19, White Ian. 3, Crandall Aug. 19, 

